With a few tips on MySQL and a brief SQLite tutorial, this page on the souptonuts SourceForge project page (from Mike Chirico).

It's a pretty good sized document full of little hints and tips on the use of MySQL and how you can squeeze the most out of your databases (about 35 tips in all). Off of his main page, he also has a SQLite tutorial that's pretty comprehensive and shows you how to do things like create triggers, logging inserts/updates/deletes, using the "attach" command, displaying information in a "spreadsheet format", and even defining custom user functions.

Thanks to PHP Magazine for the pointer...